DD15 Engine Bad Injector Symptoms and Ways to Fix

The DD15 is a powerful 6-cylinder diesel engine. It is used in heavy-duty trucks from Daimler, Freightliner, and Mitsubishi Fuso HD. American heavy-duty diesel engine manufacturer Detroit Demand produces the DD15. They originally released the DD15 engine in 2008, and it has since had several improvements, with the most recently released version being the 5th generation.

For this article, we are looking at the DD15s fuel injector. Specifically, this piece explores the symptoms of bad DD15 fuel injectors, some of the causes, and how you can fix them. Before that, we will briefly look at the DD15's fuel injection system.

Overview of the DD15 Fuel Injection System

Fuel injection systems are crucial for the functioning of any diesel engine. The DD15 uses a common rail injection system for fuel injection. But it is not a conventional common rail system. Instead, they utilize an Amplified Common-Rail System (ACRS) for fuel injection.

ACRS enables complete fuel injection at any engine speed. ACRS also allows fuel injection at up to five injectors for each combustion cycle. In addition, it can manage the fuel delivery rate during one injection event. Also, ACRS enables advanced fuel pressure control based on current engine operating conditions. With ACRS, the DD15 can achieve better fuel economy, emissions, and noise control than a conventional common rail system.

The DD15s fuel injector system operates at very high pressures of more than 30,000 Pounds Per Square Inch (PSI) despite its somewhat low rail pressure. The fuel injection system of the DD15 engine includes a high-pressure pump, six fuel injectors, and a rail system. Also, the Engine Control Unit (ECU) is crucial for fuel injection in the DD15.

Symptoms of a Bad DD15 Engine Fuel Injector

A bad injector in your DD15 could result in a reduction in the performance of your vehicle. It is important to be able to identify symptoms or signs of a bad injector. In this section, we delve into the signs of a bad injector in the DD15 engine. Keep in mind that other issues could cause these symptoms.

1) Check Engine Light

An obvious sign of a fuel injector problem with your DD15 engine is an illuminated check engine light in your vehicle's dashboard. There are many other problems that can trigger a check engine warning light, and a fuel injector problem is one of them. So, an issue with the rate at which the fuel injectors deliver fuel should trigger the check engine warning in your truck.

After you notice the check engine light, the next step will be to diagnose the cause using a diagnostic scan tool to pinpoint exactly why the engine light is on.

2) Misfiring Engine

A misfiring engine is when at least one of the engine's cylinders does not fire properly. Several things can cause your DD15 engine to misfire, such as the absence of chamber heat, damaged ignition coils, sensor issues, and inaccurate engine timing. A bad fuel injector can also cause this symptom to occur in your DD15-powered truck.

A worn or damaged injector will not be able to deliver the amount of fuel required by the ECU. As a result, combustion in the cylinders will be inaccurate, leading to a misfire or reduced acceleration. A clogged fuel injector can also cause misfires in the DD15 engine.

3) Leaking Fuel

Diesel leaking from your DD15 is a potential symptom of a fuel injector problem. A clear sign of a leak is the smell of diesel when driving your truck. The fuel leaks can occur at the point where the injector connects to the fuel rail or on the injector body. The likelihood of a fuel leak around the injectors increases with age.

Another sign beyond the smell that diesel fuel is leaking in your DD15 is faster fuel consumption in your engine. Inspect the injector for any leaks.

4) DD15 Engine Cranks Without Starting

There is an entire process from starting the ignition to the engine starting. All the components performing those processes need to be on point for the DD15 engine to start. Right in the midst of those processes is the fuel injector, which introduces fuel into the cylinders. If the fuel injector is bad, the necessary amount of fuel that should go into the cylinders for combustion won't, and the DD15 will not start.

If the injectors are bad, you might hear the cranking sound from the starter motor as it turns the crankshaft without the engine starting. A related symptom is needing to crank the engine repeatedly before it starts up.

5) Engine Rough Idle, Stalling or Loss of Power

A bad injector in the DD15 may cause it to rough idle, stall, or lose power. Rough idling is when a stationary vehicle shakes or vibrates excessively with the engine on. Clogged and leaking fuel injectors will prevent adequate amounts of fuel from reaching the cylinder when idling. Also, a clogged injector may not atomize the fuel properly, which will cause poor fuel distribution in the cylinders leading the DD15 to rough idle.

Secondly, a bad injector can cause your DD15 engine to stall. Engine stalling is when the engine shuts down unexpectedly when it is running. A common cause is the fuel delivery system, which includes the fuel injectors. A bad injector can affect the correct flow of diesel for combustion leading to engine stalling.

A bad injector may also lead to a loss of power. A loss of power is when the DD15 does not reach its full power or expected revolutions per minute when you accelerate.

6) Decreased Fuel Economy

If the fuel injector in your DD15 is bad, you may experience a reduction in the fuel economy of your truck or vehicle. A bad injector, as we have noted, can cause bad or mistimed combustion. Incorrect combustion will lead to an increase in the DD15's fuel consumption.

In case you find yourself topping up your vehicle with fuel more frequently than you are used to, the DD15s engine's fuel injector could be bad.

7) Increased Emissions

Bad injectors may cause your DD15 to emit more harmful greenhouse gases than is safe or expected. A DD15 injector that is stuck open will allow more fuel than is necessary into the DD15s cylinders. This situation will lead to increased burning and emission of smoke from the exhaust.

A strong smell or visible black smoke from the exhaust could be an indication that there is an issue with your DD15 engine's fuel injector.

Causes of DD15 Engine Injector Problems

Most of the fuel injector symptoms discussed above are caused by some specific issues with the injectors or injection system. We want to take a look at some of the common causes of bad fuel injector symptoms.

1) Stuck Injector

Many of the symptoms discussed are the result of the injectors remaining stuck. Normally the ECU manages the opening and closing of the fuel injectors. However, certain things can force the injectors to remain open or closed. For example, foreign materials like dirt and water can affect the open and closed state of the fuel injector.

2) Clogged Injector

Just like dirt and debris can affect the open or closed state of the DD15s injector, they can also block the flow of fuel through them. An accumulation of particles over time will affect the injection of fuel into the DD15s cylinders leading to some of the symptoms of a faulty injector discussed. The injectors are more likely to be clogged if the fuel filter is not in its best condition.

3) Wear

Like with all mechanical components, an injector will lose its abilities as it ages. Engines that have clocked higher mileage are more likely to see their parts wither and wear out faster. The same will happen to fuel injectors with time. But even without heavy use, the DD15s injectors will wear out at some point.

How To Fix a Bad DD15 Injector

Fixing a fuel injector problem in the DD15 can take many turns, depending on the issue. A damaged injector can either be reconditioned or replaced. The condition of the injector will determine the best step to take.

Reconditioning a bad DD15 injector will involve removing the injector and completely disassembling it. The injector will then be intensely inspected for issues. After, the injectors will be cleaned and rebuilt. Finally, the injectors will be tested to ensure they meet the necessary standards. Testing will help determine the durability of a reconditioned injector.

There are situations where reconditioning, repairing, or a rebuild of the fuel injector will be inadequate. An old and worn or severely damaged injector may be beyond rebuilding or cleaning. You will need to replace such an injector to get rid of the symptoms you have been experiencing.

Replacing the injectors can be a complicated task. Besides replacing them, you will also need to program the new injectors. As such, we recommend consulting with a service center for the repair or replacement of a bad injector.

Further, you should understand that the DD15s injectors themselves may not be bad. Instead, some other component in the fuel injection system might be causing the symptoms you are experiencing. The fuel pump, common rail, fuel rail, or ECU could be the source of the problem. As such proper diagnosis of the problem needs to be done before considering any solutions.

A great way to prevent DD15 injector-related symptoms is to frequently perform maintenance routines on your engine in line with the manufacturer's instructions. In addition, make sure you use high-quality diesel fuel for your DD15-powered vehicle.

Conclusion

In this piece, we have examined the symptoms of a bad injector in a DD15 engine. Some of the symptoms we have identified include the check engine warning light, misfiring engine, fuel leak, and the engine cranking without starting. Other symptoms to be mindful of include engine idling, stalling or power loss, increased emissions, and reduced fuel economy.

Some of the causes of these symptoms range from stuck, worn, and clogged injectors. Fixing a bad DD15 injector will involve a repair or replacement, depending on its state. Further, any of the symptoms identified could occur because of a different engine component and not the injector. Consult with an expert for a proper diagnosis of bad injector symptoms in your DD15 engine.